X-ray tube



Patented Oct. 16, 1934 Gilles noise and Albert Bouwers, Eindhoven, YNetherlandaassignors to N. V. -Philips Gloeilampenfabrreken ApplicationyMarch4 `13,

1930, Serial N0. 435,581

In the Netherlands April 19, 1929 17 claims.

This invention relates tol an improvement ifnpr modification of vacuumHchambers, generally of the type comprising X'raytubes with rotaryanticathode `as descrbedand claimedu in application il senNo. V186,522filed Aprn 25, 1927, new Patent No. 1,893,759. f

` Tubes arranged on theprinciplextherein described have the advantagethat the focal spot is not formed at the same point of the anticathode 710 for the` entire duration 'of' the load, but shifts constantly. Thus,the heating of the `anticathodes mirror ortarget isnot concentrated onaV dente'point but is distributed over a large surface area whichpermits the load'to be' of 15 greater intensity or of longer duration.

The arrangement of a rotary part within va space, having as highajvacuum as doesprevail, for instance, in X-ray tubes, entails greatdiniculty. According to the above patent, the rotation is obtained bythe use'of an-ant'icathode con- `stituting the rotor of `an electricmotor and, in the form of construction (described in the said "patent,the rotor is journalled on `a pair of ballbearings. vThis form ofconstruction has, how- 2'5 ever, been found to present` disadvantages.

The various metal parts arranged withinfthe tube must be substantiallydeprivedjof occluded gases. The driving off ofthe occludedgas'es iseffected by heating these parts to a very Vhigh temperature. Suchheating is,- however, injurious to the ball bearings on which the rotarypart revolves. Furthermore, the heating of the device lduring itsoperation causes the rotation to'take -place less evenly andless lightlythan might be j expected when using ballv bearings.

Ithas now been found that morev favorable results areobtained if,instead of using ball bearings "for the support of the anticathodicbody, one or more slide-blocks are used, in which case an ,40' aperturedbearing-disk secured to 'the `rotor surrounds a stationarvmember whichmember has a smaller coefficient of expansion and, preferably, `agreaterhardness than `the bearing=disk- A suitable disk for thispurposeconsists of a copper- S llgraphitey alloycontfainingv about 1% ofcarbon.

The content ofcarbonmay vary between -about 0.5 and A3%. *The materialon whichfthis disk `bears ispreferably tungsten, molybdenum, or 'ametalof similar hardness. Itisrpreferable that,

` :150 1ofthe Vsurfaces slidinglinconta'ct with each other,

thesurface of the harder material extendsbeyond Atheother. Thereby it ispreventedthat, by wear, the harder material grinds grooves intothesofter :material which mighti hinder an I easy rotation.

'Pf-1a order that the' invention may tf-eieany (Cl.` Z-35) l understoodand readily carried into effect one form of construction of a vacuumchamber acccrdingto the invention, represented by an X-ray tube, will bedescribed more fully with reference to the accompanying drawing, inwhich;

f Figure 1 is a partly sectionized side view of an YX-ray tube accordingto the invention.

Figure v2 is a sectional side View, on an enlarged scale, of theanticathode of the tube.

In the two figures, like parts are designated by similar referencenumerals.

Referring to Figure 1, the wall of the tubel has two glass parts 1-1 anda cylindrical metal part 3,r preferably of ferrochrorne, sealed betweenthe glass parts. The glassparts 1 and 1 are sur- 76 rounded byrenvelopes 2 2 consisting of an insulating material which is hardlytransparent to X-rays; The cylindriealmetal part 3 comprises a window 4which allows active X-ra-ys to emerge. The tube has an incandescentcathode 5 arranged 75 within a metal receptacle 6 comprising an aperture9 which allows the electrons emitted by the incandescent cathode to passto an anticathode 3. The two ends of the incandescent cathode areconnected to contact pins 7; one by means of a 80 pole wire, the otherthrough the metal receptacle 6 (not shown). The lead wires for the powersupply to the cathode may be connected to the Vsaidcontact pins.

Ihe cathode rays are concentrated on a small 85 part of the end surfaceof the anticathode Sby the focussing device 6.

'The anticathode 8 is adapted to rotate within the X-ray tubeand forthis purpose it constitutes the rotor ofan electric motor andis pivotedto a stationary shaft; This shaft is formed of a spindle 10 anda sleeve12' clamped around it. Thespindle 10 is integral with'a member 11hermetically sealed to the glass wall 1 of the tube.

rlihe `member 11 preferably consists of ferroy95 chrome and is connectedto a connecting member 2 0. The anticathode has a sheath 13 formed ofgood conducting material, preferably of copper, which surrounds acylinder 14 of metal of high permeability, such as soft iron.

The tube is surrounded bythe stator 15 of the motor. Thejlatter issecured to ahousing 16 which niechanicallyand electrically connects themagnet system to the metal part Bof theX-ray tube. The stator '15carries magnet windings 17, 105 which may be connected' to a `supplycircuit .of polyphasealternatng current or, when means to Vestablish aphase difference are provided, to an ordinary source of alternatingcurrent. .'Thus, lthe anticathode 8, as the rotor ofan asynchro` li()given a rotary 21 and 22. The sliding surfaces of the member 12 extendbeyond those of the disks 21 and 22.l Thus the latter have an even wearand the harder material does not grind in them grooves which in courseof time are injurious to the proper working. In the alloy of which themetals'21 and '22' consist, the graphite provides for lubrication whichensures a very light and noiseless running, even after long use. i

It is, of course, obvious that the invention, once disclosed,has-numerous applications in vacuum chamber practice, even where a spacedischarge does not occur. Accordingly, it is vint ended 'that theinvention be limited only by the scope of the appended claims.

1. As part of a vacuum tube, a stationary shaft, a hollow anodeconcentric with and encircling the said shaft, and rotatable thereabout,at least one bearing member on the said anode cooperating with thesaidshaft, the shaft having a surface formed of harder material than saidmember.

2. As'part of a vacuum tube, a stationary shaft, a hollow anodeconcentric with and encircling the said' shaft, and rotatable-thereabout at least 'one bearing memberl on the said anode cooperatingwith the said shaft, the shaft having .a surface formed of material oflower coefficient-of expansion than the said member.

3. As part of a'vacuurn tube, a stationary shaft, a hollow anodeconcentric with and encircling the said stationary shaft and rotatablethereabout, and atleast one bearing member on the anodeand cooperatingwith the said shaft, the

shaft having a surface formed of harder material than the said member,and the bearing member material. I y

4. As part of a vacuum tube, a stationary'shaft, a hollow anodeconcentric with:and encircling the said stationary shaft andV rotatablethereabout, and at least one bearing member on Vth'e yanode andcooperating with the said shaft,l the'V 1 shaft having a surface formedof harder material than the said'member, and the bearing member`-beingformed ofan alloy of copper and carbon.l

5. As part of a vacuum tube, a stationary shaft,

` a hollow anode concentricwith and encircling the' said 'stationaryshaft and rotatable thereabout, and at least one Vbearing member on Vtheanode and cooperating with the said shaft, the shaft having a surfaceformed of harder material than the said member, and thev bearing memberbeing formed of an alloy of copper and approximately 0.5 to 3% carbon.

6. As part of a vacuum tube, a stationary shaft,

"a hollow'anode concentric with and-encircling `the said stationaryshaft about, and at least one bearing member on the and rotatablethereanode and cooperating with thesaid` shaft, .fthe shaft havingafsurface formed of harder material than the said member, and thebearing meinber being formed of an alloy containing Vapproximately 1%carbon. ,A 7. As part of a vacuum tube,-a stationaryshaft,

yshaft having a surface formed of material harder harder thanand havinga lower coeflicient of ex- -aholl'owanode concentric with and encirclingformedof harder material than the said memabove V.the said shaftlimitingthe longitudinal movement of the bearing member and the anodesecuredtheretO, the

shaft, ae'hlollow anode vcircling 'the said stationary shaft androtatable vsaid shaft having a material :thanthe saidbearing members,andthe thef 'saidn shaft and adaptedto substantially'abut gthe innerfaces of the said Vbearing `membersfrto y limit the longitudinalmovementthereof, the said a hollow anode concentric with and encirclingthe said stationary shaft, and rotatable thereabout, and at least onebearing member on the said anode and cooperating with the said shaft,the

than and having a lower coeflicient of expansion than Vthat from whichthe said bearing member isformed.'

8'. As part of a vacuum tube, a stationary shaft, a hollow anodeconcentric with and encircling the said stationary shaft, and rotatablethereabout, and at least one bearing member on the said anode andcooperating with the said shaft, the shaft having a surface formed ofmaterial pansionthan that from which the said bearing member-is formed,the said bearing member being formed of `a self-lubricating alloy.

9. As part of a vacuum tube, a stationary shaft,

,the said. vshaft and rotatable thereabout, landat leastlone bearingmember on theanode cooperating With'and bearing against the said shaft,the said shaft extending outwardly beyond the said bearing member andits surface being formed i of harder material than the said member.

10. As part Yof a Vvacuum tube,` a stationary shaft, a hollow anodeconcentric with and encircling the said stationary shaft, and aplurality of bearing members on the said anode and co-l operating with`and bearing against the said shaft, the said shaft extending outwardlybeyond the said bearing members and its surface being bers. e Y

11. As'part of a vacum tube, astationary shaft, a hollow anodeconcentric with and encircling the said stationary shaft and rotatablethereabout, lat least one bearing member on Vthe said anodeV andcooperating with and bearing against the said shaft, and an annularshoulder and bearing against and shaft having'Y a surface formed ofharder mate- 7120 rial .than the said bearingmember. being formed ofanalloy containing a lubricating f 12, As part of a vacuum tube, astationary concentric with and enthereabout, twobearing members securedto the said anode and` cooperatingv with and bearing against the saidshaft, two annular shoulders on .the said shaft andadapted tosubstantiallyv abut the'inner faces of the said bearing members to limitthe longitudinal movement thereofLthef surface formed of harder said.bearing members lubricatingalloy.

13. As lpartvrof a vacuumV tube, a stationaryv shaft, a hollow anodevconcentric with and encircling Vthe said stationary shaft and rotatablethereabout, two bearing members. Vsecured, to the said, anode ,andvcooperating withv and bearing against the said'shaft, two annularshoulders on being vformed of la selfshaft vextending outwardly fromVandr'beyond the saidAVV bearing members, andhaving a surface.A`

o formed of harder material. than the said bearing members, and the'saidbearing membersl being formed of itself-lubricating alloy. y

1 1. 4In a-vacuum tube, a hollow anode formed placed over a hollow coreof magnetically permeable material, a target seated in the said anode,concentric, apertured disks fixed in thesaidanode, a stationary shaftabout which the said disks are adapted to rotate adjacent the endsthereof, and shoulders on the said Vshaft limiting the position ofthedisks by abutment against their inner faces, the shaft having a surfaceformed of harder material than the said disks, and the shaft extendingoutwardly beyond each disk.

15. In a vacuum tube, a rotor member supported by a sliding bearingcomprising a bushing which consists of an alloy of copper and graphite.secured to said member and surrounding a stationary member of lowercoefficient of expansion and greater hardness than said bushing.

